JP7341782B2 - Angle detection device - Google Patents

Description

The present invention relates to an angle detection device, and particularly to an angle calculation device that calculates a swing angle from a reference posture of a mirror that swings around a swing axis.

There are known scanning devices that emit light toward a predetermined area while deflecting it, and detect the light that returns from the predetermined area, thereby obtaining various information about objects located within the predetermined area. There is. In such a scanning device, a movable mirror such as a MEMS (Micro Electro Mechanical System) mirror is provided as a part that deflects light.

In a scanning device having such a movable mirror, the outgoing light is deflected by changing the angle of the mirror to change the incident direction and reflection direction of the light beam with respect to the mirror. Therefore, in order to know where in a predetermined area the emitted light is irradiating, it is necessary to detect the angle of the mirror with respect to the reference attitude.

As a method for detecting the angle of a mirror, for example, a strain sensor installed in the movable part of the mirror detects the deformation of a part of the movable part as the magnitude of distortion, and the angle of the mirror is detected by using the piezoresistive effect or piezoelectric effect. The angle of the angle is calculated. Furthermore, a method has been proposed in which the angle of the mirror is detected by irradiating light onto the mirror and using a quadrant detector to detect a change in the reflection direction of the light reflected by the mirror (for example, Patent Document 1) .

Japanese Patent Application Publication No. 2012-198511

As mentioned above, the method of calculating the mirror angle using the detection results of the strain sensor uses changes in the physical properties of the material in the movable parts, etc., so the detection sensitivity is temperature dependent, and the repeated strain Detection sensitivity changes due to material deterioration caused by this phenomenon. For this reason, there was a problem in that the angle of the mirror could not be calculated with high accuracy.

Furthermore, in the method of detecting the angle of the mirror by utilizing the change in the direction of reflection of the light reflected by the mirror as in the above-mentioned prior art document, it is necessary to make the light incident on the mirror at a relatively angle. A considerable amount of space is required in the direction perpendicular to the light reflecting surface of the mirror. For this reason, the required volume around the mirror increases, and the presence of a laser, a detector, etc. that irradiates light for angle detection causes a problem in that the light scanning area by the scanning device is limited.

As described above, one example of a problem in detecting the angle of a mirror using a strain sensor is that accurate calculation cannot be performed due to temperature dependence and time measurement deterioration of the material. Additionally, when detecting the angle of a mirror based on changes in the direction of reflected light from the mirror, a large space is required to install a detector, etc., which limits the scanning area of the scanning device. This is an example of a problem.

The present invention has been made in view of the above points, and one of its objects is to provide a space-saving angle detection device that is resistant to changes in the surrounding environment and changes over time.

The invention according to claim 1 has a first surface that reflects light and a second surface located on the opposite side of the first surface, and the invention includes a first surface that reflects light, and a second surface that is located on the opposite side of the first surface, and that is configured to swing around a swing axis from a reference posture. a mirror configured to be movable; a light source that emits a laser beam that travels parallel to the second surface of the mirror in the reference posture; and a light source that is on the optical path of the laser beam that is emitted from the light source and travels. The present invention is characterized in that it includes a photodetector provided and an angle calculation section that calculates a swing angle from the reference posture based on the light reception result of the photodetector.

The invention according to claim 9 has a first surface that reflects light and a second surface located on the opposite side of the first surface, and the invention includes a first surface that reflects light, and a second surface that is located on the opposite side of the first surface, and that rotates around a swing axis from a reference posture. a mirror configured to be movable; and a laser beam directed from outside of a region located directly below the second surface in a direction passing through the region when viewed from a direction perpendicular to the first surface of the mirror in the reference posture. A light detection device comprising a light source that emits light and a light receiving surface that receives the laser light that has passed through the area, and arranged so that the amount of the laser light received by the light receiving surface changes with the rocking of the mirror. and an angle calculation unit that calculates a swing angle of the mirror from the reference attitude based on the light reception result of the photodetector.

FIG. 1 is a diagram showing the overall configuration of an angle detection device according to the present embodiment. FIG. 2 is a cross-sectional view of the angle detection device according to the present embodiment. FIG. 3 is a diagram schematically showing how laser light is irradiated in a reference posture of a mirror. FIG. 7 is a diagram schematically showing how laser light is irradiated when the mirror is tilted toward the first photodetector. FIG. 6 is a diagram schematically showing how laser light is irradiated when the mirror is tilted toward the laser light emitting section. It is a graph showing the relationship between the light intensity detected when the mirror swings and time. It is a graph showing the relationship between normalized light intensity and swing angle. It is a figure which shows typically the case where the laser beam reflected by the mirror injects into a 1st photodetector. FIG. 7 is a diagram schematically showing how laser light is irradiated in a modified example. FIG. 3 is a diagram schematically showing the relationship between the phase difference between the waveform of a drive signal and the tilt of a mirror. FIG. 7 is a top view schematically showing how a laser beam passes through a part of the back surface of a mirror in a modified example. FIG. 7 is a cross-sectional view schematically showing how a laser beam passes through a part of the back surface of a mirror in a modified example. FIG. 7 is a diagram schematically showing how a detector receives reflected light obtained by reflecting laser light on a tilt detection mirror in a modified example. It is a figure which shows typically the shape of the mirror and the light receiving part in a modification. It is a figure which shows typically the shape of the mirror and the light receiving part in a modification. It is a figure which shows typically the shape of the mirror and the light receiving part in a modification. It is a figure which shows typically the shape of the mirror and the light receiving part in a modification. It is a figure which shows typically the shape of the mirror and the light receiving part in a modification. It is a figure which shows typically the shape of the mirror and the light receiving part in a modification.

Preferred embodiments of the present invention will be described in detail below. In the following description of the embodiments and the accompanying drawings, substantially the same or equivalent parts are designated by the same reference numerals.

FIG. 1A is a perspective view showing the overall configuration of an angle detection device 10 according to this embodiment. The angle detection device 10 is a device that detects a swing angle (hereinafter also referred to as swing angle) of a mirror that swings around a swing axis from a reference posture.

The angle detection device 10 includes a MEMS mirror 10 that deflects light, a laser light emitting section 21 that emits a laser beam, a first photodetector 22 and a second photodetector 23 that receive the laser beam, and a first photodetector 22 and a second photodetector 23 that receive the laser beam. It has an angle calculation unit 24 that calculates the swing angle of the MEMS mirror 10 based on the light reception results of the detector 22 and the second photodetector 23.

The MEMS mirror 10 is a MEMS (Micro Electro Mechanical System) mirror that includes a mirror that deflects light by periodically swinging. The MEMS mirror 10 includes a support section 11 and a movable section 12 that is swingably supported by the support section 11. The support portion 11 is fixed to a casing portion (not shown).

The movable part 12 has a mirror part 13 supported by the support part 11 in a swingable state around a swing axis CA. The mirror section 13 is connected to and supported by the support section 11 by a torsion bar 14 extending along the swing axis CA. Note that the support portion 11 and the movable portion 12 are made of a semiconductor material, and can be formed by processing a semiconductor wafer, for example.

A light reflecting surface is formed on the first main surface of the mirror section 13. On the other hand, the second main surface of the mirror section 13, which is the main surface on the opposite side to the first main surface, has a black color and has been subjected to anti-reflection processing such as providing fine grooves. . Further, a permanent magnet (not shown) is provided on the second main surface of the mirror section 13. When a magnetic field is applied to the permanent magnet so that the torsion bar 14 is twisted in its circumferential direction, the mirror section 13 swings around the swing axis CA while being supported by the support section 11.

The mirror unit 13 swings around the swing axis CA with a basic attitude in which the first main surface and the second main surface are supported so as to be horizontal. In this embodiment, the mirror section 13 periodically swings within a predetermined angle range around the reference posture. For example, if the clockwise direction from the normal direction of the first principal surface in the basic posture is defined as a + direction, and the counterclockwise direction is defined as a - direction, then The angle AG between the normal line and the normal line in the reference posture periodically swings within the range of AG≦±θmax (for example, ±15°). In the following description, the maximum angle θmax indicating the limit of the swing angle will also be referred to as the maximum swing angle.

The laser beam emitting section 21 is provided on the second main surface side of the mirror section 13 in the reference attitude. For example, the laser beam emitting unit 21 is located outside the MEMS mirror 10 (that is, in a direction parallel to the second main surface of the mirror unit 13 in the reference posture, the distance from the center of the mirror unit 13 is longer than the outer edge of the MEMS mirror 10 A laser beam is emitted from a far position) so as to pass over the second main surface of the mirror section 13.

The first photodetector 22 is composed of a photodiode such as an APD (Avalanche PhotoDiode). The first photodetector 22 is provided on an optical path along which the laser light emitted from the laser light emitting section 21 travels through the second main surface of the mirror section 13 . For example, the first photodetector 22 is located on the second main surface side of the mirror section 13 in the reference attitude, and is located on the mounting area of the MEMS mirror 10 (i.e., on the first main surface side of the mirror section 13 in the reference attitude). It is provided at a position facing the laser beam emitting section 21 with the area directly below the MEMS mirror 10 (when the second main surface side is defined as "upper" and the second principal surface side is "lower") sandwiched therebetween.

The second photodetector 23, like the first photodetector 22, is composed of a photodiode. The second photodetector 23 receives the laser beam reflected at the end of the mirror section 13 when the mirror section 13 swings in one direction, and when the mirror section 13 swings in the other direction, the laser beam is incident on the second photodetector 23. is provided at a position where the laser beam does not enter. For example, the second photodetector 23 is disposed on the second main surface side of the mirror section 13 in the reference attitude and at a position close to the laser beam emitting section 21.

The angle calculation unit 24 calculates the angle of the mirror unit 13 with respect to the reference attitude based on the light reception result of the first photodetector 22. Further, the angle calculation section 24 detects in which direction the mirror section 13 is tilted from the reference posture based on the light reception result of the second photodetector 23.

FIG. 1B is a cross-sectional view of the angle calculation device 100 taken along the XX line. Here, the positional relationship of each part is shown when the mirror part 13 is in the standard posture.

The laser beam emitting section 21 is configured to emit a laser beam from the outside of the outer edge of the MEMS mirror 10 toward the center of the mirror section 13 on the second principal surface S2 side of the mirror section 13 . It is arranged with the exit facing in the direction of. A lens 25 is provided close to the front side of the emission aperture of the laser beam emission section 21 (that is, on the side in the direction toward the center of the mirror section 13).

The first photodetector 22 has a light receiving surface in the direction of the center of the mirror section 13 so as to receive the laser light emitted from the laser light emitting section 21 and passing on the second main surface of the mirror section 13. It is placed towards.

The second photodetector 23 is arranged in a direction facing the second main surface S2 of the mirror section 13 so as to receive the laser beam emitted from the laser beam emitting section 21 and reflected at the side end of the mirror section 13. The sensor is placed with the light-receiving surface facing the

Next, the angle detection operation performed by the angle detection device 100 of this embodiment will be described with reference to FIGS. 2A, 2B, 2C, 3A, and 3B.

FIG. 2A is a diagram schematically showing how laser light is emitted and received when the mirror section 13 is in the standard posture. Here, a direction perpendicular to the first main surface S1 and the second main surface S2 of the mirror section 13 is shown as a normal line NL. The laser beam LL (indicated by a broken line in FIG. 2A) emitted from the laser beam emitting section 21 passes through the lens 25 and travels parallel to the second main surface S2 of the mirror section 13, The light is incident on the photodetector 22. The amount of laser light LL incident on the first photodetector 22 is the largest compared to the state in which the mirror section 13 is oscillated. That is, in this state, the light intensity detected by the first photodetector 22 becomes maximum.

FIG. 2B shows a state in which the first main surface S1 of the mirror section 13 is tilted in the direction in which the first photodetector 22 is located from the reference posture shown in FIG. 2A, that is, the normal NL is tilted in the direction A in FIG. 2A. A state in which the mirror portion 13 is tilted so as to change is shown. In this state, a part of the laser light LL emitted from the laser light emitting section 21 is irradiated onto the second main surface S2 of the mirror section 13, and its progress is hindered. Therefore, the amount of laser light LL that enters the first photodetector 22 is smaller than when the mirror section 13 is in the reference attitude.

FIG. 2C shows a state in which the first main surface S1 of the mirror section 13 is tilted in the direction in which the laser beam emitting section 21 is located from the reference posture shown in FIG. 2A, that is, the normal NL changes in the direction B in FIG. 2A. The mirror portion 13 is shown tilted as shown in FIG. In this state, a portion of the laser beam LL emitted from the laser beam emitting section 21 is irradiated onto the first main surface S1 or the side end portion of the mirror section 13, and its progress is hindered. Therefore, the amount of laser light LL that enters the first photodetector 22 is smaller than when the mirror section 13 is in the reference attitude. Further, of the laser beam LL emitted from the laser beam emitting section 21 , the laser beam reflected at the side end of the mirror section 13 on the side of the laser beam emitting section 21 enters the second photodetector 23 .

Next, a method in which the angle calculation unit 24 shown in FIG. 1 calculates the swing angle of the mirror unit 13 based on the light reception result of the first photodetector 22 and the light reception result of the second photodetector 23 will be described.

FIG. 3A is a graph showing the relationship between the swing angle of the mirror section 13, the light intensity of the laser light detected by the first photodetector 22 and the second photodetector 23, and time. Here, the light intensity of the laser light detected by the first photodetector 22 is shown as D1, and the light intensity of the laser light detected by the second photodetector 23 is shown as D2.

When the mirror section 13 is in the standard attitude (denoted as swing angle SA=0), the light intensity of the laser light detected by the first photodetector 22 is maximum. On the other hand, the swing angle of the mirror part 13 is the maximum, that is, the angle between the normal NL of the first main surface SL of the mirror part 13 and the normal NL direction of the first main surface S1 in the reference attitude is the maximum swing angle. In a certain state (shown as swing angle SA=max), the light intensity of the laser light detected by the first photodetector 22 is at a minimum. In this way, since the value of the detected light intensity changes depending on the swing angle, the angle calculating section 24 can calculate the swing angle based on the magnitude of the light intensity.

Furthermore, when the mirror section 13 is tilted in the direction A shown in FIG. 2A, the laser beam does not enter the second photodetector 23, and when the mirror section 13 is tilted in the direction B shown in FIG. Laser light enters the vessel 23. As shown as D2 in FIG. 3A, the light intensity of the laser beam is detected by the second photodetector 23 only when the laser beam is tilted in one direction. Therefore, the angle calculating section 24 can determine the direction of inclination of the mirror section 13 based on whether the light intensity of the laser beam is detected by the second photodetector 23.

The angle calculation unit 24 uses the normalized light intensity that is normalized based on the maximum value of the light intensity of the laser light detected by the first photodetector 22 as the normalized light intensity, and calculates the normalized light intensity and swing angle obtained in advance. The swing angle of the mirror section 13 is calculated from the relationship.

Next, a formula for calculating the normalized light intensity will be explained. Here, the maximum swing angle of the mirror section 13 is 15 degrees, and when the swing angle is at its maximum, the first photodetector is detected when looking from the laser beam emitting section 21 toward the first photodetector 22. An example will be explained in which the outer edge of the mirror section 13 is in contact with the lower end of the light receiving section of the device 22.

First, assuming that the mirror section 13 is a circular mirror with a diameter of dmm, the lower half of the first main surface S1 of the mirror section 13 (that is, the possibility that the laser beam emitted from the laser beam emitting section 21 will enter) is The area of the part) is S=(d ² /8)π.

When the mirror section 13 is swung and tilted, if the angle between the normal direction of the first principal surface S1 and the normal direction in the reference posture is θ, then the laser beam is The area of the portion that blocks the is expressed as S(θ)=(d ² /8)πsinθ.

If the laser beam is incident on the first principal surface S1 of the mirror section 13 when θ=15°, then the portion of the laser beam emitted from the laser beam emitting section 21 that is not blocked by the mirror section 13 The light amount I(θ) is expressed by the following Equation 1 (Equation 1).

Here, I ₀ is the amount of laser light that enters the first photodetector 22 when the mirror section 13 is in the standard posture. By dividing this light amount I(θ) by _I0 , a normalized light intensity “normalized light intensity I(θ)” as expressed by the following Equation 2 (Equation 2) is obtained.

FIG. 3B is a graph showing the relationship between normalized light intensity and swing angle. In the swing angle range of ±15°, the value of the normalized light intensity changes linearly in accordance with the change in the swing angle.

The angle calculation unit 24 calculates the normalized light intensity based on the light intensity of the laser beam detected by the first photodetector 22, and calculates the swing angle based on the relational expression shown in Equation 2 above. . By using the above-mentioned formula for calculating the normalized light intensity, the swing angle of the mirror section 13 can be stabilized regardless of the maximum light intensity value (i.e., the light intensity when the mirror section 13 is in the reference posture). It can be calculated by

As described above, in the angle detection device 100 of the present embodiment, the angle calculation section 24 calculates the swing angle of the mirror section 13 based on the light intensity of the laser beam detected by the first photodetector 22. Further, the angle calculation unit 24 determines in which direction the mirror unit 13 is tilted based on whether the second photodetector 23 detects a light intensity equal to or higher than a predetermined value.

According to this configuration, unlike the case where the angle is calculated using a strain sensor, the swing angle of the mirror section 13 can be calculated without being affected by temperature dependence or material deterioration over time. . Therefore, it is possible to stably and accurately calculate the swing angle.

Further, the laser beam emitting section 21, the first photodetector 22, and the second photodetector 23 are provided on the side opposite to the light reflecting surface of the mirror 10 (that is, on the second main surface side of the mirror section 13). , the laser beam is emitted and received in a direction parallel to the second principal surface of the mirror section 13 in the reference attitude. Therefore, since not much space is required in the direction perpendicular to the light reflecting surface of the mirror 10, the angle detection device can be configured in a small space.

That is, according to the angle detection device of this embodiment, it is possible to realize angle detection that is space-saving and resistant to changes in the surrounding environment and changes over time (that is, robust).

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, the second main surface of the mirror section 13 is black and provided with fine grooves in order to prevent reflection of laser light on the second main surface of the mirror section 13. An example was explained. However, the present invention is not limited to this, and it is sufficient that an anti-reflection structure is formed on the second main surface of the mirror section 13. For example, fine protrusions may be formed on the second main surface, or paint with low reflectance may be applied. Conversely, the mirror portion 13 itself may be formed of a material with low reflectance, and only the first principal surface may be processed to have reflectivity.

Further, in addition to the anti-reflection processing described above, a configuration may be further provided to suppress the laser beam reflected by the second main surface of the mirror section 13 from entering the first photodetector 22. good.

FIG. 4A is a diagram schematically showing how the laser beam reflected by the second main surface of the mirror section 13 enters the first photodetector 22. In this way, when the laser beam reflected by the second main surface of the mirror section 13 enters the first photodetector 22, the laser beam emitted from the laser beam emitting section 21 directly hits the first photodetector 22. Since the light intensity reflected by the second principal surface of the mirror section 13 and incident on the first photodetector 22 is added to the incident light intensity, there is a possibility that the angle cannot be calculated. .

FIG. 4B is a diagram schematically showing a configuration for suppressing the laser beam reflected by the second main surface of the mirror section 13 from entering the first photodetector 22. A second lens 26 is provided between the side end of the mirror section 13 near the first photodetector 22 and the first photodetector 22 . Further, a shielding body 27 having an opening (aperture) is provided between the second lens 26 and the first photodetector 22.

The laser beam reflected by the second main surface of the mirror section 13 is focused by the second lens 26 at a position different from the opening of the shielding body 27. Therefore, the laser beam does not pass through the opening of the shielding body 27 and does not enter the first photodetector 22. On the other hand, laser light (hereinafter referred to as The parallel light (referred to as parallel light) is focused by the second lens 26 at the position of the opening of the shielding body 27 . Therefore, the laser beam enters the first photodetector 22. According to this configuration, it is possible to restrict the incidence of the laser beam reflected by the second main surface of the mirror section 13 on the first photodetector 22, and to allow only parallel light to enter the first photodetector 22. Therefore, it becomes possible to accurately detect the angle.

Further, in the above embodiment, an example was described in which the light reception result of the second photodetector 23 is used to determine which side the mirror portion 13 is tilted to. However, different from this, for example, a configuration may be adopted in which a strain sensor is provided in the movable part 12 and the method of inclination is determined using a piezoresistance effect or the like. Although the sensor results of the strain sensor are affected by temperature dependence and material deterioration over time, the accuracy of angle calculation is not necessary for determining which side the mirror section 13 is tilted to. Therefore, the determination can be made using a strain sensor.

In addition, when a rotational torque is directly applied to the MEMS mirror 10 and the mirror section 13 is oscillated with resonance or non-resonance (for example, when a permanent magnet is bonded to the second main surface of the mirror section 13 and (in the case where the mirror is oscillated by a magnetic field), it is possible to determine the direction of inclination of the mirror portion 13 based on the waveform of the drive voltage or drive current.

FIG. 5 is a diagram showing the relationship between the waveform of the drive signal and the rocking of the mirror section 13. For example, in the case of direct drive type resonance operation, the mirror unit 13 generates a magnetic field according to the drive signal from a magnetic field generation source to which a drive signal including a resonance frequency is applied, and the magnetic field acts on the permanent magnet. As a result, the mirror section 13 swings in a resonant state. In this swinging operation, the swinging of the mirror section 13 has a waveform whose phase is delayed by 90° compared to the waveform of the drive signal, as shown in FIG. Therefore, it is possible to determine the direction of inclination of the mirror section 13 based on the drive signal on the premise that the phase is delayed by 90 degrees.

Further, the swing angle of the mirror section 13 can be detected by the angle detection device of the above embodiment without using the entire second main surface of the mirror section 13. FIG. 6A is a top view schematically showing how the laser beam emitted from the laser beam emitting section 21 travels along a part of the second main surface of the mirror section 13, and FIG. 6B is a cross-sectional view thereof. It is. In this way, by arranging the laser beam emitting section and the first photodetector so as to calculate the angle using the laser beam that has passed through a part of the second main surface of the mirror section 13, the angle of the mirror section 13 can be adjusted. Even when the permanent magnet 30 is fixed to the second main surface, it is possible to calculate the angle without being affected by the permanent magnet 30.

Further, in the above embodiment, an example was described in which the first photodetector 22 directly receives the laser beam emitted from the laser beam emitting section 21. However, it may be configured such that the first photodetector 22 receives light after the laser light is once reflected by a mirror or the like. FIG. 7 is a diagram showing an angle detection device having such a configuration. A tilt detection mirror 21 is provided at a position facing the laser beam emitting section 21 with the mounting area of the MEMS mirror 10 interposed therebetween. The photodetector 32 is provided at a position where the laser beam reflected by the tilt detection mirror 21 is incident. Also in the angle detection device having such a configuration, it is possible to calculate the swing angle of the mirror section 13 based on the light intensity of the laser beam detected by the photodetector 32, as in the above embodiment.

Further, in the above embodiment, the case where the mirror portion 13 is circular has been described as an example, but the shape of the mirror portion 13 is not limited to this. For example, the mirror portion 13 may have a square shape, such as a square or a rectangle.

FIGS. 8A to 8F are diagrams schematically showing the relationship between the light receiving surface of the first photodetector 22 and the portion where the laser beam is blocked by the mirror section 13 as seen from the laser beam emitting section 21. .

FIG. 8(A) shows that the mirror part 13 is circular as in the above embodiment, and the mirror part 13 is in the most inclined state (that is, the state in which the swing angle is the maximum), and the edge of the mirror part is in the first position. A case is shown in which the light-receiving surface of the photodetector 22 comes into contact with the lower side thereof. The above-mentioned formula for calculating the normalized light intensity is based on the assumption that the mirror portion 13 is circular as described above. However, by using a different formula for calculating the normalized strength, it is possible to calculate the swing angle of the mirror section 13 even when the mirror section 13 has a square shape, for example.

When the mirror part 13 has a square shape, in a state where the mirror part 13 blocks a portion of the laser beam from progressing as shown in FIG. 8(B), the first light detection part Since the amount of laser light incident on the mirror 22 changes, the swing angle of the mirror section 13 can be calculated based on the change in light intensity. However, as shown in FIG. 8(C), the mirror portion 13 almost completely blocks the progress of the laser beam, and further, as shown in FIG. 8(D), the mirror portion 13 When the laser beam protrudes, the amount of laser light incident on the first photodetector 22 does not change, so it becomes impossible to calculate the swing angle of the mirror section 13 based on the light intensity. Therefore, as shown in FIG. 8(E), the light-receiving surface of the first photodetector 22 is made large so that even when the mirror section 13 is at its most inclined, it does not completely cover the first photodetector 22. Thereby, even when the shape of the mirror portion 13 is square, it is possible to sufficiently calculate the swing angle. Furthermore, the progress of the laser beam may be prevented from being completely blocked by the mirror section 13 by enlarging the area of the laser beam irradiation region using a lens or the like. Furthermore, as shown in FIG. 8(F), even when the mirror section 13 is circular, the light-receiving surface of the first photodetector 22 is made large, so that the area where the progress of the laser beam is blocked by the mirror section 13 is reduced. You can do it like this.

Furthermore, the series of processes described in the above embodiments can be performed by computer processing according to a program stored in a recording medium such as a ROM.

100 Angle detection device 10 MEMS mirror 11 Support part 12 Movable part 13 Mirror part 14 Torsion bar 21 Laser beam emission part 22 First photodetector 23 Second photodetector 24 Angle calculation part 25 Lens 30 Permanent magnet 31 Mirror for tilt detection 32 Photodetector

Claims (10)

a mirror having a first surface that reflects light and a second surface located on the opposite side of the first surface, and configured to be swingable around a swing axis from a reference posture;
a light source that emits a laser beam that travels parallel to the second surface of the mirror in the reference posture;
a photodetector provided on the optical path of the laser beam emitted from the light source and traveling;
an angle calculation unit that calculates a swing angle from the reference posture based on the magnitude of light intensity when the light is received by the photodetector;
An angle detection device characterized by having: The angle calculation unit compares the magnitude of the light intensity when the light is received by the photodetector with the magnitude of the light intensity when the mirror is in the reference posture, thereby determining the swing from the reference posture. The angle detection device according to claim 1, wherein the angle detection device calculates an angle. The angle calculation unit normalizes the light intensity of the laser beam detected by the photodetector using the light intensity detected by the photodetector when the mirror is in the reference attitude, and The angle detection device according to claim 1 or 2, wherein the swing angle from the reference posture is calculated based on a normalized light intensity that is a normalized light intensity. a second photodetector provided at a position where the laser beam enters when the mirror swings in one direction from the reference posture, and where the laser light does not enter when the mirror swings in the other direction; has
4. The angle calculation unit determines a swing direction of the mirror from the reference posture based on a light reception result of the second photodetector . Angle detection device. The mirror has a permanent magnet fixed to the second surface, and oscillates to resonate with a magnetic field generated by a magnetic force generation source that operates upon application of a drive signal;
The angle detection device according to any one of claims 1 to 3, wherein the angle calculation unit determines a swing direction of the mirror from the reference posture based on a signal waveform of the drive signal. . 6. The angle detection device according to claim 1, wherein an antireflection structure is formed on the second surface of the mirror. Disposed between the light source and the photodetector, the laser beam reflected on the second surface of the mirror and the laser beam that has proceeded without being reflected on the second surface are placed at different positions. A lens that focuses light,
It is characterized by having a shielding part that is provided close to the light-receiving surface of the photodetector and that shields at least a part of the laser light that is reflected by the second surface of the mirror and focused by the lens. An angle detection device according to any one of claims 1 to 6. a second mirror that reflects the laser beam that has passed on the second surface of the mirror;
8. The angle detection device according to claim 1, wherein the photodetector is arranged at a position where it can receive the laser beam reflected by the second mirror. a mirror having a first surface that reflects light and a second surface located on the opposite side of the first surface, and configured to be swingable around a swing axis from a reference posture;
a light source that emits a laser beam in a direction passing through the region from outside the region located directly under the second surface when viewed from a direction perpendicular to the first surface of the mirror in the reference posture;
a photodetector having a light-receiving surface that receives the laser light that has passed through the region, and arranged so that the amount of the laser light received by the light-receiving surface changes as the mirror swings;
an angle calculation unit that calculates a swing angle of the mirror from the reference posture based on the magnitude of light intensity when the light is received by the photodetector;
An angle detection device characterized by having: a mirror having a first surface that reflects light and a second surface located on the opposite side of the first surface, and configured to be swingable around a swing axis from a reference posture;
a light source that emits a laser beam that travels parallel to the second surface of the mirror in the reference posture;
a photodetector provided on the optical path of the laser beam emitted from the light source and traveling;
an angle calculation unit that calculates a swing angle from the reference posture based on the light reception result of the photodetector;
Angle detection characterized in that the angle calculation unit calculates a swing angle from the reference attitude by comparing a light reception result of the photodetector with a light reception result when the mirror is in the reference attitude. Device.

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